The present invention relates to a rotary cutting tool for making holes in walls made from thermoplastic materials or the like, particularly of containers such as car fuel tanks, with a tool body having a rotation axis as the tool axis and which for cutting out a hole disk carries a cutting member projecting freely in the direction of the tool axis with a cutting edge radially spaced from the latter.
Car petrol tanks are being increasingly produced according to the thermoplastic blowing process. After shaping by blowing air into an injection opening, further machining must take place on the tank prior to its fitting in the motor vehicle, e.g. it must be provided with a plurality of holes, which are e.g. required for the fitting of a tank pick-off, a venting nipple, etc. Smaller holes have hitherto been made as bores with a twist drill, whereas larger diameter bores are made with a cutting member constructed in the manner of a turning tool, whose cutting edge is at right angles to the tool axis or approximately parallel to the correspondingtank wall and is consequently at right angles to the rotation direction in such a way that by machining, it cuts an annular groove in the corresponding tank wall until the hole disk formed within said annular groove is completely separated from the wall and consequently a hole is formed, whose diameter corresponds to the external diameter of the turning tool. Both cutting tools suffer from the disadvantage that they can only function in a cutting manner, i.e. during the production of the hole chips and possibly cutting powder occur, whereof at least a small portion regularly passes into the tank if the holes are made overhead, because said chips and the cutting powder tend, as a result of electrostatic charging, to adhere to the tank and consequently immediately or during the further machining thereof pass through the holes and into the tank. When subsequently a vehicle engine is supplied with fuel from the tank, such chips inevitably lead to operating problems.